Protective layer(s) in organic image sensors

ABSTRACT

The present disclosure relates to an organic image sensor and an associated method. By inserting an inorganic protective layer between an electrode and an organic photo active region of the image sensor, the organic photo active region is protected from moisture, oxygen or following process damage. The inorganic protective layers also help to suppress the leakage in the dark. In some embodiments, the organic image sensor comprises a first electrode, an organic photoelectrical conversion structure disposed over the first electrode and a second electrode disposed over the organic photoelectrical conversion structure. The organic image sensor further comprises a first protective structure covering a top surface and a sidewall of the organic photoelectrical conversion structure.

REFERENCE TO RELATED APPLICATION

This Application is a Continuation of U.S. application Ser. No.14/316,946 filed on Jun. 27, 2014, the contents of which areincorporated by reference in their entirety.

BACKGROUND

Digital cameras and other digital imaging devices use arrays of millionsof tiny photodetectors or pixels to record an image. For example, when acameraman or camerawoman presses his or her camera's shutter button andexposure begins, each photodetector in the array is uncovered to detectthe presence or absence of photons at the individual array locations. Toend the exposure, the camera closes its shutter, and circuitry in thecamera assesses how much light (e.g., how many photons) fell into eachphotodetector while the shutter was open. The relative quantity orintensity of photons that struck each photodetector are then storedaccording to a bit depth (0-255 for an 8-bit pixel). The digital valuesfor all the pixels are then stored and are used to form a resultantimage.

Conventional solid state image sensors are made up of an array ofphotodetectors which individually include PN junctions made ofsemiconductor material, for example, silicon disposed in a semiconductorsubstrate. Color filter arrays (CFAs) with separate color filters forred, blue, and green light are often arranged over photodetector arraysto differentiate between different colors of light. When an incidentlight ray has a large angle of incidence, the light can easily passthrough one color filter into other neighboring color filters and/orother neighboring photodetectors underneath the color filters. Thus, ashield or re-direct element is inserted between photodetectors ofdifferent colors to reduce the crosstalk between photodetectors ofdifferent color filters, which otherwise will ultimately cause noisethat distorts the resultant digital images.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIG. 1A illustrates a cross-sectional view of some embodiments of anorganic image sensor.

FIG. 1B illustrates a cross-sectional view of some other embodiments ofan organic image sensor.

FIG. 2 illustrates a cross-sectional view of some other embodiments ofan organic image sensor.

FIG. 3 illustrates a top view of some embodiments of an organic imagesensor.

FIG. 4 illustrates a flow diagram of some embodiments of a method offorming an organic image sensor.

FIGS. 5A-F illustrate some embodiments of cross-sectional views of amethod of forming an organic image sensor.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the provided subjectmatter. Specific examples of components and arrangements are describedbelow to simplify the present disclosure. These are, of course, merelyexamples and are not intended to be limiting. For example, the formationof a first feature over or on a second feature in the description thatfollows may include embodiments in which the first and second featuresare formed in direct contact, and may also include embodiments in whichadditional features may be formed between the first and second features,such that the first and second features may not be in direct contact. Inaddition, the present disclosure may repeat reference numerals and/orletters in the various examples. This repetition is for the purpose ofsimplicity and clarity and does not in itself dictate a relationshipbetween the various embodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. The apparatus may be otherwise oriented (rotated 90 degreesor at other orientations) and the spatially relative descriptors usedherein may likewise be interpreted accordingly.

One type of solid state image sensor is an organic CMOS image sensor(CIS) that includes an organic photoelectrical conversion structurearranged between upper and lower electrodes. When incident radiation ofsufficient energy strikes the organic photoelectrical conversionstructure, an electron-hole pair is created. Due to a bias appliedacross the electrodes, the hole is accelerated toward one of theelectrodes (e.g., towards the lower electrode acting as an anode), whilethe electron is accelerated toward the other electrode (e.g., towardsthe upper electrode acting as a cathode). In this way, the incidentradiation produces a photocurrent between the electrodes, wherein thecurrent level of this photocurrent is proportional to the intensity ofthe incident radiation absorbed.

To help decrease leakage, some organic CISs include electron-blockingand/or hole-blocking layers between the organic photoelectricalconversion structure and the various electrodes. For example, ahole-blocking layer can be inserted between the organic photoelectricalconversion structure and the cathode (e.g., upper electrode) to hinderholes moving from the cathode to the organic photoelectrical conversionstructure. Similarly, an electron-blocking layer can be inserted betweenthe organic photoelectrical conversion structure and the anode (e.g.,lower electrode) to hinder electrons moving from the anode to theorganic photoelectrical conversion structure. Thus, these electron/holeblocking layers can help to decrease leakage and improve efficiency ofthe cell. Unfortunately, in previous approaches, an electron- orhole-blocking layer is formed directly over an exposed surface of theorganic photoelectrical conversion structure so the electron- orhole-blocking layer abuts the exposed surface of the organicphotoelectrical conversion structure. In particular, this overlyingelectron- or hole-blocking layer is deposited by plasma vapor deposition(PVD), and this plasma process can damage the exposed surface of theorganic photoelectrical conversion structure, thereby degrading theperformance of the CIS.

Therefore, to ward off this potential PVD-damage, some embodiments ofthe present disclosure include one or more protection layers to helpprotect the surface of the organic photoelectrical conversion structurefrom plasma damage. In addition, in some embodiments, one or moreprotection layers are included to increase the electron- orhole-blocking capability of an electron- or hole-blocking layer betweenthe organic photo active layer and the lower electrode.

Further, the organic photoelectric conversion structure may compriseorganic conjugated materials that are easily degraded by reacting withoxygen and moisture. By covering the organic photoelectric conversionstructure by these protection layers, reliability of the organic imagesensor is improved. Thus, these protection layer(s) can help improve theoverall performance, reliability, and/or efficiency of the CIS.

FIG. 1 a shows a cross-sectional view of some embodiments of an organicimage sensor 100, which includes first and second protection structures108, 118 that are described in more detail below. The organic imagesensor 100 includes an organic photoelectrical conversion structure 120arranged between a first (lower) electrode 104, and a second (upper)electrode 114. The second electrode 114 is transparent in apredetermined wavelength range so photons 130 having wavelengths fallingwithin a predetermined wavelength range pass through the secondelectrode 114 to strike to the organic photoelectrical conversionstructure 120. For example, the second electrode 114 can be made of atransparent conductive metal oxide such as ITO, FTO, AZO, IGZO, SnO2and/or ZnO. When incident radiation of sufficient energy passes throughthe upper electrode 114 and is absorbed by the organic photoelectricalconversion structure 120, an electron-hole pair is created. A voltage isapplied across the first and second electrodes 104, 114 so generatedholes are accelerated toward one of the electrodes (e.g., towards thelower electrode 104 acting as an anode), while electrons are acceleratedtoward the other electrode (e.g., towards the upper electrode acting asa cathode). In this way, the incident radiation produces a photocurrentbetween the electrodes 104, 114, wherein the current level of thisphotocurrent is proportional to the intensity of the incident radiationabsorbed.

First and second charge-blocking layers 106, 116, which block oppositetypes of charge, separate the organic photoelectrical conversionstructure 120 from the first and second electrodes 104, 114,respectively. The second charge blocking structure 116 is transparent inthe predetermined wavelength range to allow photons having wavelengthsfalling within the predetermined wavelength range to strike to theorganic photoelectrical conversion structure 120. For example, inembodiments where the first electrode 104 acts as an anode, the firstcharge-blocking layer 106 is an electron-blocking layer. Similarly, inembodiments where the second electrode 114 acts as a cathode, the secondcharge-blocking layer 116 is a hole-blocking layer. It will beappreciated that the anode and cathode could be flipped in otherembodiments, such that the lower electrode 104 can alternatively act asa cathode while the upper electrode 114 can act as an anode, providedapplied biases and polarities of the charge-blocking layers are alsoflipped.

Whatever the precise arrangement, the electron blocking structure (e.g.106) comprises material having a higher “lowest unoccupied molecularorbital” (LUMO)/conduction band (CB) energy than a work function of theanode. The electron blocking structure 106 can work as a holetransporting structure as well and the electron blocking structure(e.g., 106) may correspondingly have an electro affinity smaller than awork function of the material of the anode (e.g., first electrode 104)and an ionization potential smaller than the ionization potential of theadjacent organic photoelectrical conversion structure 120. For example,the electron blocking structure may comprise an inorganic material, suchas MoO₃, NiO, WO₃, CuO or V₂O₅, for example. Similarly, the holeblocking structure (e.g. 116) comprises material having a lower highestoccupied molecular orbital (HOMO)/valence band (VB) energy than a workfunction of the cathode. The hole blocking structure 106 can work as anelectron transporting structure as well and the hole blocking structure(e.g., 116) may correspondingly have an ionization potential large thana work function of the cathode (e.g., second electrode 114) and anelectron affinity larger than the electron affinity of the adjacentorganic photoelectrical conversion structure 120. For example, the holeblocking structure may comprise an inorganic material, such as LiF,TiO₂, ZnO, Ta₂O₅ or ZrO₂, for example.

A first protective structure 118 is disposed over the organicphotoelectrical conversion structure 120. The first protective structure118 is disposed between the second charge blocking structure 116 and theorganic photoelectrical conversion structure 120 and covers a topsurface and a sidewall of the organic photoelectrical conversionstructure 120. The first protective structure 118 can be formed by ALD.In some embodiments, the first protective structure comprises aluminumoxide (Al₂O₃), aluminum nitride (AlN), or silicon oxide (SiO₂). Thefirst protective structure 118 has a thickness in a range of from about5 Å to about 5 nm

In some embodiments, the image sensor 100 further comprises a secondprotective structure 108 disposed between the first electrode 104 andthe first charge blocking structure 106. The second protective structure108 can comprise the same material as or a different material than thefirst protective structure 118. The second protective structure canenhance electron/hole blocking of the first charge blocking layer 106.

In some embodiments, the organic photoelectric conversion structure 120is made up of an upper organic charge blocking layer 120 a, a lowerorganic charge blocking layer 120 b, and an organic photo active layer120 c. The organic photo active layer 120 c may comprise one or moresemiconducting, conjugated polymers, alone or in combination withnon-conjugated materials. For example, the organic photo active layer120 c may comprise fullerene derivative (e.g. PTB7 and PC71BM). Theorganic photo active layer 120 c may comprise a blend of two or moreconjugated polymers or organic molecules with similar or differentelectron affinities and electronic energy gaps. The organic photo activelayer 120 c may also comprise a series of hetero-junctions utilizinglayers of organic materials or the blends. The upper and/or lowerorganic charge blocking layers 120 a, 120 b can manifest as an electronblocking layer (or somewhat analogously as a hole transport layer) madeup of Poly(3-hexylthiophene-2,5-diyl) (P3HT),Poly(3,4-ethylenedioxythiophene) Polystyrene sulfonate (PEDOT:PSS) orPoly[2-methoxy-5-(3′,7′-dimethyloctyloxy)-1,4-phenylenevinylene](MDMO-PPV). The upper and/or lower organic charge blocking layers 120 a,120 b can also manifest as a hole-blocking layer (or somewhatanalogously as an electron transport layer) made up of fullerenederivative and one or more than one n-type conjugated polymer. Forexample, the organic hole-blocking/electron transport layer can comprise2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP),2,2′-(1,3-Phenylene)bis[5-(4-tert-butylphenyl)-1,3,4-oxadiazole](OXD-7), Tert-butyl Peroxyisobutyrate (TBPi) or3-(Biphenyl-4-yl)-5-(4-tert-butylphenyl)-4-phenyl-4H-1,2,4-triazole(TAZ).

As shown in FIG. 1B, in some other embodiments, the second protectivestructure 108′ can be disposed between the first charge blockingstructure 106′ and the organic photoelectrical conversion structure 120.

In some embodiments, some of the inorganic blocking structures 106, 116are formed by physical vapor deposition (PVD) which may introduce plasmadamage to the organic photoelectric conversion structure if formeddirectly onto the organic photoelectric conversion structure. In someembodiments, by forming the protective structure 118 and/or 108 throughchemical vapor deposition (CVD) method, in particular atomic layerdeposition (ALD), the organic photo electric conversion structure 120 isprotected from plasma damage as well as from moisture and otherenvironmental contaminants.

FIG. 2 shows another example of an organic image sensor 200 inaccordance with some embodiments. The organic image sensor 200 is madeup of a plurality of individual optical sensors 242 (which can also bereferred to as “pixels”). For convenience, FIG. 2 illustrates threepixels 234, 236 and 238, which will be described below as a red pixel234, a green pixel 236, and a blue pixel 238. It will be appreciatedthat although FIG. 2 illustrates three pixels 234-238, optical sensorsin accordance with this disclosure can include any number of pixels,ranging from a single pixel to billions or even more pixels. Further,the pixels are often arranged to follow a predetermined pattern, such asin a Bayer filter for example, where green pixels are arranged tocorrespond to one half of a checkerboard pattern and where the red andblue collectively establish the other half of the checkerboard pattern.See e.g., FIG. 3. Patterns other than that of a Bayer filter could alsobe used.

Each pixel 242 includes multiple layers which are stacked on top of oneanother, and which are formed by photolithography techniques and/or byspin-on coatings, for example. The structure of each pixel 242 islargely the same and repeated. The organic image sensor 200 comprises afirst electrode structure 204 (which may also be referred to as a “pixelelectrode array” in some embodiments), an organic photoelectricconversion structure 220 disposed over the first electrode array 204, afirst protective structure 218 disposed over the organic photoelectricconversion structure 220, a second electrode structure 214 (which mayalso be referred to as an “upper transparent electrode” in someembodiments) disposed over the first protective structure 218, and acolor filter array 210 disposed over the second electrode structure 214.The organic photoelectric conversion structure 220 is configured toconvert one or more photons having wavelengths falling with apredetermined wavelength range into an electrical signal.

In some embodiments, the organic photoelectric conversion structure 220comprises an organic photo active layer, a p type organic hole transportlayer and a n type organic electron transport layer. The secondelectrode structure 214 is transparent in the predetermined range. Insome embodiments, the first electrode structure 204 can comprise metaland the second electrode structure 214 can comprise at least one of:ITO, FIO, AZO, or IGZO. One or both of the first and the secondelectrode structures 204 and 214 are an electrode array having separatecomponents for each pixel 242. The first protective structure 218 isdisposed between the organic photoelectric conversion structure 220 andthe second electrode structure 214 and covers a top surface and aperimeter of the organic photoelectric conversion structure 220. In someembodiments, the first protective layer 218 covers sidewalls of theorganic photoelectric conversion structure 220 to protect the organicphotoelectric conversion structure 220 from moisture and oxygen and/orfrom plasma damage. In some embodiments, the organic image sensor 200further comprises some inorganic charge blocking structures to suppressthe leakage in the dark. For example, an inorganic hole blockingstructure 216 can be disposed between the first protective structure 218and the second electrode structure 214 to prevent a hole from movingfrom the second electrode structure 214 to the organic photoelectricalconversion structure 220. Although the pixels 242 are similar in manyrespects, the pixels differ from one another in that the correspondingcolor filter provides different wavelength specificity. Each colorfilter of the color filter array 210 passes light of a predeterminedfrequency range there through, while blocking light of other frequencyranges. For example, the red pixel 234 includes a red color filter 210a, which allows red light to pass there through while blocking otherwavelengths of light (e.g., red color filter 210 a blocks blue and greenlight). The green pixel 236 includes a green color filter 210 b thatallows green light there through while blocking other wavelengths oflight (e.g., green color filter 210 b blocks red and blue light). Theblue pixel 238 includes a blue color filter 210 c that allows blue lightto pass there through while blocking other wavelengths of light (e.g.,blue color filter 210 c blocks red and green light).

During operation, polychromatic light approaches the optical sensor 200as shown by arrow 230, and strikes the upper surfaces of the colorfilters 210 at a substantially normal angle of incidence, for example.The polychromatic light 230 is filtered to contain only a narrowspectrum of light as it passes through each color filter 210. Thisfiltered light then passes through the upper transparent electrodes 214and through transparent charge-blocking structure 216 and strikes thephotoelectric conversion layers 220. In the photoelectric conversionlayer 220, the light is converted from a photon or electromagnetic waveinto an electrical signal, such as a voltage or current. The voltagelevel or current level, which is established between the first andsecond electrodes 204, 214, corresponds to the intensity of light thatstrikes the photoelectric conversion layer 220 for a given pixel. Thiselectrical signal is then passed down through interconnect structures222 to read out circuitry 224 formed in a substrate 226. In someembodiments, the read out circuitry 224 can be a CMOS circuitry. Thesubstrate 226 can be a semiconductor substrate, a plastic substrate orany other suitable substrates. The read out circuitry 224 then uses analgorithm, such as a demosaicing algorithm, to generate a digital imagefrom the electrical signals provided by the array of pixels.

FIG. 4 shows a flow diagram of some embodiments of a method 400 offorming an organic image sensor. While disclosed methods (e.g., methods400) are illustrated and described below as a series of acts or events,it will be appreciated that the illustrated ordering of such acts orevents are not to be interpreted in a limiting sense. For example, someacts may occur in different orders and/or concurrently with other actsor events apart from those illustrated and/or described herein. Inaddition, not all illustrated acts may be required to implement one ormore aspects or embodiments of the description herein. Further, one ormore of the acts depicted herein may be carried out in one or moreseparate acts and/or phases.

At 402, a first electrode layer is formed over a substrate.

At 404, an electron blocking layer is formed over the first electrodelayer.

At 406, an organic photoelectrical conversion layer is formed over theelectron blocking layer.

At 408, a portion of the organic photoelectrical conversion layer isremoved to form a recess that circumscribes at a perimeter of an organicphotoelectrical conversion structure.

At 410, a conformal protective structure is formed over the organicphotoelectrical conversion structure covering a top surface and fillingthe removal perimeter portion of the organic photoelectrical conversionstructure covering a sidewall of the organic photoelectrical conversionstructure.

At 412, a hole blocking layer is formed over the conformal protectivestructure. In some embodiments, the hole-blocking layer is formed byPVD, and the protection layer formed in 410 protects the organicphotoelectrical conversion structure from this PVD process.

At 414, a second electrode layer is formed over the hole blocking layer.

FIGS. 5 a-5 h show some embodiments of cross-sectional views ofprotection barrier structure showing a method of forming protectionbarrier for an integrated microsystem.

Although FIGS. 5 a-5 h are described in relation to method 400, it willbe appreciated that the structures disclosed in FIGS. 5 a-5 h are notlimited to such a method.

As shown in FIG. 5 a, a first electrode layer 504 is formed over asubstrate 502. For example, the substrate 502 can be a semiconductorsubstrate, for example, silicon, or a plastic substrate and the firstelectrode layer 504 can be made of metal, such as silver, gold,aluminum, titanium, copper, platinum, palladium, and/or nickel. Thefirst electrode can also be made of metal nanowire, a carbon nanotubesor a conductive polymer. A surface treatment can be performed and anadhesion assisting layer can be prepared to the substrate 502 to improvethe adhesion property of a coating solution. In some embodiments, thesubstrate 502 is transparent at a predetermined wavelength range, suchthat light strikes the sensor through the bottom face of the substrate502a. For example, the substrate 502 can be made of glass or resin. Inthis alternative case, the first electrode layer 504 can be made of atransparent conductive metal oxide such as ITO, FTO, AZO, IGZO, SnO2and/or ZnO. A transparent substrate, if present, is not particularlylimited and known materials having any shape, structure, thickness andthe like can be used. The first electrode 504 has a thickness in a rangeof from about 50 nm to about 200 nm.

As shown in FIG. 5 b, an electron blocking layer 506 is formed over thefirst electrode layer 504. In some embodiments, a second protectivelayer 508 can be formed between the first electrode layer 504 and theelectron blocking layer 506. The electron blocking layer 506 cancomprise PEDOT:PSS, high K (MoO₃, NiO, CuO, WO₃, V₂O₅). The electronblocking layer 506 can have a thickness in a range of from about 5 nm toabout 20 nm. The second protective layer 508 can have a bandgap largerthan 3 eV. The second protective layer 508 can comprise Al₂O₃, AlN, orSiO₂. The second protective layer 508 can have a thickness in a range offrom about 0.5 nm to about 10 nm.

As shown in FIG. 5 c, an organic photoelectrical conversion layer 520 isformed over the electron blocking layer 506. In general, the organicphotoelectric conversion layer 502 comprises a p-type layer and ann-type layer. In some embodiments, the p-type layer directly abuts then-type layer to form a p-n junction, but in other embodiments anintrinsic layer is arranged between the p- and n-type layers to form aPIN junction. The p-type layer helps hole transport and can compriseP3HT, MDMO-PPV or other applicable material having a thickness in arange of from about 5 nm to about 20 nm. The n-type layer helps electrontransport and can comprise fullerene derivative and one or moreconjugated polymers having a thickness in a range of from about 5 nm toabout 20 nm. The organic photoelectrical conversion layer 520 canfurther comprise an active layer comprising conjugated polymers andfullerene derivatives (e.g. PTB7 and PC71BM). The organicphotoelectrical conversion layer 520 can have a thickness in a range offrom about 100 nm to about 500 nm.

As shown in FIG. 5 d, a portion of the organic photoelectricalconversion layer 520 is removed to form a recess 550 that circumscribesat a perimeter of an organic photoelectrical conversion structure 520′.

As shown in FIG. 5 e, a conformal protective structure 518 is formedover the organic photoelectrical conversion structure 520′ covering atop surface and filling the removal perimeter portion 550 of the organicphotoelectrical conversion structure 520′ covering a sidewall of theorganic photoelectrical conversion structure 520′. The conformalprotective structure 518 is formed by ALD at a relative low temperature.The conformal protective structure 518 can have a bandgap larger than 3eV. The conformal protective structure 518 can comprise Al₂O₃, AlN, orSiO₂. The conformal protective structure 518 can have a thickness in arange of from about 0.5 nm to about 10 nm. The conformal protectivestructure 518 can be made of same or different material with the secondprotective structure 508.

As shown in FIG. 5 f, a hole blocking structure 516 is formed over theconformal protective structure 518. A second electrode structure 514 isformed over the hole blocking layer 516. The hole blocking layer 516 cancomprise LiF, TiO₂, ZnO, Ta₂O₅ or ZrO₂. The hole blocking layer 516 canhave a thickness in a range of from about 5 nm to about 20 nm. Thesecond electrode structure 514 can be made of a transparent conductivemetal oxide, metal bulk, metal nanowire, a carbon nanotubes or aconductive polymer. Notably, The first and second electrode structures504 and 514 work as a cathode and an anode can be switchable along withthe electron blocking structure 506′ and the hole blocking structure516, according to the device structure. The thin film protectivestructures 508 and 518 fabricated by CVD can be disposed coveringsurfaces of the organic photoelectrical conversion structure 520′ tohelp suppress the dark current and decrease damage introduced by thefollowing processes.

In some embodiments, the present disclosure relates to an organic imagesensor. The organic image sensor comprises an organic photoelectricalconversion structure arranged between a first electrode and a secondelectrode, and configured to convert photons into an electrical signal.The organic image sensor further comprises a first charge blockingstructure arranged between the first electrode and the organicphotoelectrical conversion structure and configured to block a firstkind of electric charge. The organic image sensor further comprises asecond charge blocking structure arranged between the organicphotoelectrical conversion structure and the second electrode andconfigured to block a second kind of electric charge. The organic imagesensor further comprises a first protective structure arranged betweenthe second charge blocking structure and the organic photoelectricalconversion structure.

In other embodiments, the present disclosure relates to an organic imagesensor. The organic image sensor comprises an organic photoelectricalconversion structure configured to convert photons having wavelengthsfalling within a predetermined range into an electrical signal. Theorganic image sensor further comprises an upper electrode disposed overthe organic photoelectrical conversion structure, wherein the upperelectrode is transparent to the photons have wavelengths falling withina predetermined range. The organic image sensor further comprises afirst protective structure disposed between the upper electrode and theorganic photoelectrical conversion structure.

In yet other embodiments, the present disclosure relates to a method offorming an organic image sensor. The method comprises forming a firstelectrode layer over a substrate, and forming an organic photoelectricalconversion structure over the first electrode layer. The method furthercomprises forming a protective structure covering a top surface of theorganic photoelectrical conversion structure using an atomic layerdeposition process. The method further comprises forming a first chargeblocking layer configured to block a first type of charge over theprotective structure, and forming a second electrode layer over thefirst charge blocking layer

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

What is claimed is:
 1. An organic image sensor, comprising: an organic photoelectrical conversion structure arranged between a first electrode and a second electrode, and configured to convert photons into an electrical signal; a first charge blocking structure arranged between the first electrode and the organic photoelectrical conversion structure and configured to block a first kind of electric charge; a second charge blocking structure arranged between the organic photoelectrical conversion structure and the second electrode and configured to block a second kind of electric charge; and a first protective structure arranged between the second charge blocking structure and the organic photoelectrical conversion structure.
 2. The organic image sensor of claim 1, wherein the first protective structure extends along sidewalls of the organic photoelectrical conversion structure.
 3. The organic image sensor of claim 1, further comprising: a second protective structure arranged between the second charge blocking structure and the organic photoelectrical conversion structure.
 4. The organic image sensor of claim 3, wherein the second protective structure is a same material with the first protective structure.
 5. The organic image sensor of claim 1, wherein sidewalls of the first electrode are laterally offset from sidewalls of the second electrode.
 6. The organic image sensor of claim 1, further comprising: a plurality of interconnect structures, wherein the first electrode is positioned between the organic photoelectrical conversion structure and the plurality of interconnect structures.
 7. The organic image sensor of claim 1, wherein the photons have wavelengths falling within a predetermined range, and wherein the second electrode is transparent to the photons have wavelengths falling within a predetermined range.
 8. The organic image sensor of claim 1, wherein the first protective structure comprises aluminum oxide (Al₂O₃), aluminum nitride (AlN), or silicon oxide (SiO₂).
 9. The organic image sensor of claim 1, wherein the second charge blocking structure is configured to block holes.
 10. The organic image sensor of claim 1, wherein the first charge blocking structure is configured to block electrons.
 11. An organic image sensor, comprising: an organic photoelectrical conversion structure configured to convert photons having wavelengths falling within a predetermined range into an electrical signal; an upper electrode disposed over the organic photoelectrical conversion structure, wherein the upper electrode is transparent to the photons have wavelengths falling within a predetermined range; and a first protective structure disposed between the upper electrode and the organic photoelectrical conversion structure.
 12. The organic image sensor of claim 11, wherein the organic photoelectrical conversion structure comprises an organic photo active layer, an organic hole transport layer, and an organic electron transport layer.
 13. The organic image sensor of claim 11, wherein the first protective structure covers a top surface and sidewalls of the organic photoelectrical conversion structure.
 14. The organic image sensor of claim 11, further comprising: a lower electrode arranged between the organic photoelectrical conversion structure and a substrate; and a second protective structure arranged between the lower electrode and the organic photoelectrical conversion structure and comprising a same material as the first protective structure.
 15. The organic image sensor of claim 14, further comprising: a hole blocking structure disposed between the upper electrode and the organic photoelectrical conversion structure and configured to block holes; and an electron blocking structure disposed between the lower electrode and the organic photoelectrical conversion structure and configured to block electrons.
 16. A method of forming an organic image sensor, comprising: forming a first electrode layer over a substrate; forming an organic photoelectrical conversion structure over the first electrode layer; forming a protective structure covering a top surface of the organic photoelectrical conversion structure using an atomic layer deposition process; forming a first charge blocking layer configured to block a first type of charge over the protective structure; and forming a second electrode layer over the first charge blocking layer.
 17. The method of claim 16, further comprising: forming a second charge blocking layer configured to block a second type of charge over the first electrode layer, wherein the second charge blocking layer is formed prior to forming the organic photoelectrical conversion structure.
 18. The method of claim 16, further comprising: forming the protective structure to cover sidewalls of the organic photoelectrical conversion structure.
 19. The method of claim 16, further comprising: forming an organic photoelectrical conversion layer over the first electrode layer; removing a portion of the organic photoelectrical conversion layer to form a recess that circumscribes at a perimeter of the organic photoelectrical conversion structure; and forming the protective structure to fill the removed portion of the organic photoelectrical conversion structure.
 20. The method of claim 16, wherein the organic photoelectrical conversion structure is configured to convert photons having wavelengths falling within a predetermined range into an electrical signal; and wherein the second electrode is transparent to the photons having wavelengths falling within the predetermined range. 